Chronic/cyclic idiopathic emesis or vomiting syndrome in cats was identified in the late nineteenth century. Although infrequent vomiting by cats under certain circumstances may be acceptable, e.g., eating too fast or too much or presence of excessive hair or other foreign objects in the stomach, frequent vomiting or regurgitation without causes (“idiopathic vomiting”) can result in severe malnutrition in cats and cause damages to the gastrointestinal (GI) health of the cats. The four main characters that define idiopathic vomiting or regurgitation are: 1) three or more recurrent separated episodes of vomiting or regurgitation; 2) varying intervals of completely normal, healthy status between the episodes; 3) episodes are stereotypical with regard to the timing of onset, symptoms and durations; and 4) unknown causes of vomiting or regurgitation. Subjects susceptible to idiopathic vomiting cannot be identified by standard medical examination, including physical examination and/or blood work. In humans, idiopathic vomiting may be described as Cyclic Vomiting Syndrome (CVS), and may be associated with dehydration, injury to the GI tract (particularly the esophagus), and tooth decay (vomitus may be acidic).
The exact causes of idiopathic vomiting are not fully understood. However, it has recently been recognized that one of the potential causes in cats is related to central nervous system (CNS) disorders. There are several neurotransmitter receptors in the brain of the cats that can be triggered to stimulate or activate different biological pathways leading to emesis. Examples of such receptors include neurokinin (NK) receptors, histamine receptors, acetylcholine receptors, serotonin receptors, mu-opioid receptors, and dopamine-2 receptors. Therefore, a potential way to prevent or reduce idiopathic vomiting is to inhibit or partially block such receptors.
Certain 5-HT3a receptor antagonists, such as dolasetron, granisetron, ondansetron, and palonosetron, have demonstrated effectiveness as antiemetics in humans and have been used to manage chemotherapy-induced nausea and vomiting in cancer patients. Further, a new class of drugs known as the NK-1 receptor antagonists has been recently developed for controlling emesis in humans, which include aprepitant and maropitant, among others. However, these compounds often lead to side effects. Further, it is difficult to administer such compounds through feeding, because of their undesirable taste. Unfortunately, injection is not a convenient alternative means of administering antiemetics. When treating animals, such as cats or dogs, injection may require veterinary assistance, particularly if the animal resists the injection.
There is a continuing need for effective and more readily available treatment for preventing, reducing, alleviating, or treating idiopathic vomiting. There is also a need for treatments with lesser side effects that can be easily administered, for example, through feeding or other oral administration. These needs are particularly acute for domestic cats with a history of idiopathic vomiting.